Therapeutic or training cushions of this type are used mainly as aids for physical exercises, for example for training the feet muscles and lower leg muscles after a fracture, paralysis or immobilization of any kind, for early mobilization of tissue after an operation in order to avoid emboli, for training the spine and bottom muscles, for coordinating the various functions of the hand and arm muscles and as an exercising apparatus for the neck muscles.
The cushion is placed under the muscles to be strengthened with the patient lying, standing or sitting according to the required exercise whereby, owing to rolling, weight displacement or to pressing, the fluid is forced from one compartment of the cushion into the other. This process is periodically repeated to complete a series of exercises.
In known cushions of the type referred to above it can happen, in use, that the weld line is broken especially at the ends thereof adjacent the flow opening. As a result, the flow opening is enlarged and the resistance to fluid flow is reduced so that the intended purpose of the exercise can no longer be achieved. The resistance to flow and therewith the achievement of the user is also dependent on the pressure to which the cushion as a whole is subjected.
It is an object of the invention to provide a therapeutic or training cushion of the type referred to which is such that the resistance of the flow opening remains almost unchanged even under high stress and after long use.